.\"
.\"Copyright (c) 2010 iXsystems, Inc.
.\"All rights reserved.
.\" written by: Xin LI <delphij@FreeBSD.org>
.\"
.\"Redistribution and use in source and binary forms, with or without
.\"modification, are permitted provided that the following conditions
.\"are met:
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.\"   notice, this list of conditions and the following disclaimer.
.\"2. Redistributions in binary form must reproduce the above copyright
.\"   notice, this list of conditions and the following disclaimer in the
.\"   documentation and/or other materials provided with the distribution.
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.\"THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\"ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.Dd February 8, 2010
.Dt NVRAM 4
.Os
.Sh NAME
.Nm nvram
.Nd "non-volatile RAM"
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following line in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device nvram"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
nvram_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides access to BIOS configuration NVRAM on i386 and amd64
systems.
.Pp
PC motherboard uses a small non-volatile memory to store BIOS settings
which is usually part of its clock chip and sometimes referred as
.Dq CMOS SRAM .
This driver exposes bytes 14 through 128 of the NVRAM, or a total of
114 bytes, at offset zero of the device file
.Pa /dev/nvram .
.Pp
This driver is useful for cloning machines that shares the same hardware
configuration and need same BIOS setting tweaks.
.Sh IMPLEMENTATION NOTES
The BIOS NVRAM's bytes 16 through 31 are checksummed at byte 32.
This driver
.Em does not
take care for these checksums.
.Sh EXAMPLES
Backup existing BIOS NVRAM to
.Pa nvram.bin :
.Pp
.Dl dd if=/dev/nvram of=nvram.bin
.Pp
Restore BIOS NVRAM from
.Pa nvram.bin :
.Pp
.Dl dd if=nvram.bin of=/dev/nvram
.Sh SEE ALSO
.Xr dd 1
.Sh HISTORY
The
.Nm
device driver first appeared in
.Fx 6.4 .
.Sh AUTHORS
.An -nosplit
The
.Nm
device driver was written by
.An Peter Wemm .
This manual page was written by
.An Xin LI .
